Question

Apparently My database function can’t fetch the database?

Warning: mysqli::real_escape_string(): Couldn’t fetch database

I’ve created a custom database class which extends MySQLi.

Here’s how I’m constructing it.

public function __construct(){
    $db = new mysqli(
        DB_HOST, DB_USER, DB_PASS, DB_NAME);

    $db->select_db(DB_NAME);
    return $db;
}

I am selecting the database, aren’t I?

The code where this is happening is here:

    private static function readSession($sessionId)
    {
    global $database;
    $sessionId = session_id();
    $sessionId = $database->real_escape_string($sessionId);
    $time = time();
    $result = $database->query("SELECT sessiondata FROM sessions WHERE sessionid='$sessionId' AND expiry > $time");
    if ($result->num_rows > 0) {
        $row = $result->fetch_array();
        return $row['sessiondata'];
    }
    return "";
}

The database is being initiated before the Session Management functions are being called.

Answer 1

You say that your custom class extends mysqli. If that is the case, you need to call the mysqli __construct() in your extending constructor, without returning anything:

class YourDatabase extends mysqli {
  public function __construct() {
    // Call the mysqli constructor explictly
    parent::__construct(DB_HOST, DB_USER, DB_PASS, DB_NAME);
    // No need to call select_db() again, since default db was selected in the 
    // parent constructor

    // Don't return anything
    // the constructor returns $this, which extends mysqli
    return;
  }
}

// Use as:
$database = new YourClass();
$database->query("SELECT * FROM atable");

Extending a class means that you are using a descendent of the parent class. You do not need to instantiate an instance of the parent class, but if you need to make use of its constructor and extend its functionality, you must explicitly call parent::__construct(...) in the child class’s __construct().